76. Cryocapacitation of Alpaca (Vicugna pacos) sperm cell

Abstract

The process of sperm cryopreservation is widely used in the programs of assisted reproduction and genetic improvement of many species. One of the features in the cryopreservation process is a disturbance at the plasma membrane which leads to a premature acrosomal reaction and phosphorylation in tyrosine residues of many proteins, as well as declining in the motility, reducing the lifetime of the sperm cell. All these changes are the result of a special type of process called “cryocapacitation”, but the possible cause for this phenomenon has not been determined yet. The study of the state of phosphorylated proteins on tyrosine residues gives us information about the level of capacitation that affects the sperm cells and is used in several studies to determine the cryocapacitation. The alpaca is a domestic species of economic importance in our country. There are many techniques for managing this species in order to carry out a genetic improvement program. The aim of this study was to evaluate a possible state of cryocapacitation in cryopreserved sperm cells of alpaca; we evaluated the motility, viability, and plasma membrane integrity before and after the freezing/thawing process; the pattern of proteins phosphorylated in tyrosine residues and the ability of binding to the zona pellucida of these frozen/thawed sperm. We compared our results with those from in vitro capacitated sperm cells. The results indicate that cryopreservation directly affects motility, viability and plasma membrane because the values are always reduced in thawed sperm cells, showing that both in vitro capacitated and cryopreserved sperm offered the same pattern of proteins phosphorylated in tyrosine residues and it was observed that the number of spermatozoa bound to the zona pellucida in the case of in vitro capacitated spermatozoa was greater than that observed in cryopreserved spermatozoa, our data also confirms the ability to bind to the zona pellucida of cryopreserved sperm. Considering the combined results of all experiments, we could conclude that the cryopreserved spermatozoa of alpaca must be undergoing a process of cryocapacitation, induced by the cryopreservation process itself.